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Unit 2: Language Basics

Arithmetic negation (–) Notes
The arithmetic negation operator returns the operand multiplied by –1, effectively changing its
sign. For example, – (3 – 4) evaluates to 1. Arithmetic negation is different from the subtraction
operator, even though they both are written as a minus sign. Arithmetic negation is always unary
and before the operand. Subtraction is binary and between its operands.
Arithmetic assertion (+)

The arithmetic assertion operator returns the operand multiplied by +1, which has no effect. It
is used only as a visual cue to indicate the sign of a value. For example, +(3 – 4) evaluates to –1,
just as (3 – 4) does.
String Concatenation Operator
Manipulating string is such a core part of PHP applications that PHP has a separate string
concatenation operator (.). The concatenation operator appends the right-hand operand to the
left-hand operand and returns the resulting string. Operands are first converted to strings, if
necessary. For example:
$n = 5; $s = ‘There were ‘. $n. ‘ ducks.’; // $s is ‘There were 5 ducks’.

Autoincrement and Autodecrement Operators
In programming, one of the most common operations is to increase or decrease the value of a
variable by one. The unary autoincrement (++) and autodecrement (––) operators provide shortcuts
for these common operations. These operators are unique in that they work only on variables;
the operators change their operands’ values as well as returning a value.
There are two ways to use autoincrement or autodecrement in expressions. If you put the operator
in front of the operand, it returns the new value of the operand (incremented or decremented).
If you put the operator after the operand, it returns the original value of the operand (before the
increment or decrement). Table 2.2 lists the different operations.
Table 2.2: Autoincrement and Autodecrement Operations

Operator Name Value returned Effect on $var
$var++ Post-increment $var Incremented
++$var Pre-increment $var + 1 Incremented
$var–– Post-decrement $var Decremented
––$var Pre-decrement $var - 1 Decremented

These operators can be applied to strings as well as numbers. Incrementing an alphabetic character
turns it into the next letter in the alphabet. As illustrated in Table 2.3, incrementing “z” or “Z”
wraps it back to “a” or “Z” and increments the previous character by one, as though the characters
were in a base-26 number system.

Table 2.3: Autoincrement with Letters

Incrementing this Gives this
“a” “b”
“z” “aa”
“spaz” “spba”
“K9” “L0”
“42” “43”

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